This invention relates to drilling fluids used in the drilling of subterranean oil and gas wells as well as other drilling fluid applications and drilling procedures. The invention is particularly concerned with synthetic hydrocarbons, and especially hydrocarbon mixtures containing mostly linear olefins, preferably with carbon numbers between 14 and 18. These synthetic hydrocarbons exhibit minimal toxicity toward aquatic life and possess desirable rheological and filtration control properties for use in drilling fluids.
The use of synthetic hydrocarbons, particularly oligomerized olefins, for drilling fluids has recently been patented. For example, Mercer et al. in U.S. Pat. No. 5,096,883 disclose the use of compositions consisting essentially of branched paraffins having between 16 and 40 atoms per molecule (such as the hydrogenated dimer of 1-decene) for this use. Also, Patel et al. in U.S. Pat. No. 5,189,012 disclose the use of compositions comprising branched chain oligomers having an average molecular weight of from 120 to 1000 in drilling fluids. These synthetic hydrocarbons are prepared by oligomerizing one or more olefinic monomers having a chain length of C.sub.2 to C.sub.14. The full disclosure of these two references is incorporated herein by reference.
One well-known method for oligomerizing olefins utilizes a boron trifluoride catalyst. However, boron trifluoride is toxic and, upon contact with water or steam, produces toxic and corrosive fumes. Moreover, disposal of boron trifluoride residues presents an environmental problem.
Therefore, a novel process to produce synthetic hydrocarbons useful for drilling fluids from non-hazardous reagents utilizing a non-hazardous, non-polluting catalyst would be a significant improvement in the art.
Additionally, only a small fraction of the commercially available products of olefin oligomerization are useful in drilling fluids. Thus, the synthetic hydrocarbons used in the above-mentioned patents are often in short supply and so are not always readily available.
The long-felt need described in these patents for an environmentally acceptable, fully functional, and readily available synthetic hydrocarbon for use in synthetic hydrocarbon-based drilling fluids has not yet been satisfied; that is, not until the invention described hereinbelow.